Liquid systems, such as coating materials, varnishes, emulsion paints, and printing inks, are customarily pigmented using pigment preparations which comprise water, organic solvent or combinations thereof. In addition to anionic, cationic, nonionic or amphoteric dispersants, these pigment preparations must generally be admixed with further auxiliaries, such as humectants, agents for increasing the freeze resistance, thickeners for stabilization, biocides, and defoamers.
Such pigment preparations are employed as tinting pastes in retail stores and professional decorating businesses, and, using metering and tinting systems, are added to aqueous and solventborne inks and paints in order to set customer-specific shades. For the precise setting of a particular shade, the tinting pastes are generally metered volumetrically.
In order to comply with the guidelines for awarding of various eco labels, inks and paints have for some time advantageously been given low-VOC (volatile organic compounds) or VOC-free formulations. The same standards are also desired for the pigment preparations which are mixed in at the point of sale to the low-VOC or VOC-free inks and paints.
U.S. Pat. No. 5,340,394 teaches VOC-free pigment concentrates based on linear polyethylene glycol polyethers with molecular weights of 190 to 700 and nonionic alkyl glycosides for use at the point of sale. The pigment concentrates are described as being especially suitable for latex paints and alkyd paints, and additionally these pigment concentrates are said to be blocking-resistant.
US-A-2006/0207476 and US-A-2010/0113685 describe low-VOC universal pigment pastes which are stable, which have favorable rheology, and which are suitable for aqueous emulsion paints and for solventborne alkyd paints. The pastes may be provided in closed containers which allow simple metering in controlled quantities. These pastes contain not only solvent-compatible surfactants but also latex-compatible surfactants, such as alkyl polyethylene glycol ethers, secondary alcohol ethoxylates, difunctional propylene oxide/ethylene oxide block polymers (with secondary OH groups), ethylene oxide/propylene oxide block copolymers, alkylaryl polyglycol ethers, or amine salts of hydrophilic copolymers of polycarboxylic acids.
WO-A-2014/000842 teaches aqueous universal pigment preparations based on fatty acid condensation products and nonionic surfactants. The pigment preparations are described as being stable in their viscosity, foam, and sedimentation behavior after storage at 60° C. for one week.
WO-A-2011/151277 teaches low-VOC aqueous universal pigment preparations which are described as being suitable for preventing the drying of the preparations in open nozzles of the paint-mixing systems, and also for producing coatings of certain hardness. The pigment preparations comprise stabilizers, examples being ethoxylated fatty acid monoethanolamides, anionic surfactants based on tristyrylphenol-polyglycol ether phosphate esters, or phospholipid-based surfactants, rheological additives based on clay minerals, and also nonvolatile, organic solvents such as polyethylene glycols PEG 200 or PEG 400.
US-A-2012/0316273 describes a point-of-sale system for aqueous emulsion paints that is composed of a plurality of liquid pigment preparations which are described as being suitable for preventing the drying of the preparations in open nozzles of the metering systems. The pigment preparations comprise a polyalkylene glycol as humectant, an ethoxylated surfactant, and filler.
DE-A-102007021867 describes an aqueous pigment preparation which comprises as dispersant an anionic copolymer produced by means of a macromonomer composed of polyethylene/polypropylene glycol mono(meth)acrylic esters, where the polyalkylene glycol group contains a terminal acid group. Also present are organic solvents, such as ethylene glycol or propylene glycol.
Despite the proposals in the prior art of a multiplicity of compounds as additives for universal pigment preparations, there continues to be a need for effective additive combinations for such pigment preparations, satisfying the requirements of precise volumetric metering and at the same time the desired color properties.
Moreover, environmentally objectionable substances and also sensitizing substances ought largely to be avoided.
European directives and laws are requiring not only ever-lower VOC contents of less than 1000 ppm but also low SVOC contents (i.e., low levels of semivolatile organic compounds). Analytically, the VOC contents and SVOC contents are determined by means of GC-MS in accordance with DIN ISO 11890-2 (in-can measurement in ppm).
This therefore necessitates an entirely new assessment of the additives, since many additives undergo decomposition under the ISO 11890-2 conditions, starting at about 200° C. to 367° C. (387° C.: boiling point of C22H46 (n-docosane)), and therefore simulate a VOC and/or SVOC content.
Further requirements of European directives and laws call for the absence of additives which have an environmental hazard potential in accordance with the CLP Regulation (EC) No. 1272/2008 concerning the Classification, Labeling and Packaging of substances and mixtures. Additives with H400 hazard statements are approved only with very great restrictions for use in paints. Alkylphenyl ethoxylates (APEOs) are likewise no longer approved in EU Directive 2003/53/EC.
Furthermore, the use of the customary surfactants based on fatty alcohol alkoxylates with less than 20 alkylene oxide units, or on amino compounds, is restricted. Surfactants with H318 classification can no longer be used in the quantities needed.
Moreover, compounds having H317 classification, which may give rise to allergic skin reactions, can be used only at a maximum of 0.1 wt %.
It was an object of the present invention, therefore, to provide stable universal pigment preparations which are distinguished by ultimately advantageous performance properties, especially high color strength or easy dispersibility (capacity for stirred incorporation) in a very wide variety of application media, and/or which, over a prolonged period, exhibit no drying either in the containers or in the metering system, especially in nozzles. The pigment preparations ought also to exhibit no rubout, in the context of the coloring of the various emulsion paints and coatings.
A further object of the invention was to provide aqueous universal pigment preparations which pose a low environmental hazard, in other words preparations which are low in VOC and low in SVOC and which also contain largely no environmentally objectionable substances and sensitizing substances, in other words containing no substances liable for labeling in accordance with various eco labels, as for example in accordance with the CLP Regulation (EC) No. 1272/2008.